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Learn to distinguish the shapes of galaxies

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Wednesday, March 7, 2018 10:53 PM

Greetings, Stargazers.

This March gives us another month with two full moons and gives me a chance to complain about the popularity of calling it blue. I will have a celebration when we have the four-in-a-season, “real” blue moon next year.

Another opportunity for me to complain is the onset of daylight saving time. At least I don’t encounter the issues my wife faces when the time changes. She coordinates an online schedule of volunteers in multiple time zones and in multiple countries that start or don’t start daylight saving time on a variety of different weekends. And in the Southern Hemisphere, the switch goes the opposite direction on even different weekends. This is one thing astronomers get right – the use of universal time. I guess there are possibly fewer worries if you live in Arizona or Hawaii or some other place that doesn’t switch.

For many amateur astronomers with small telescopes, galaxy season is approaching. It has been five years since I reviewed what you can expect to see when you look for galaxies, so here is that review.

At any moderately dark site, which includes most of the Four Corners, you can see scores of these faint, fuzzy, blotches. Unfortunately, fuzzy blotches are all that one can typically see without either photographic assistance or a bigger scope. With practice, however, you can learn to distinguish all the subtle variations in the shapes of these objects.

Galaxies have historically been categorized into three very general groups – elliptical, spiral and irregular. Many people are familiar with the classic spiral galaxy shape – a flat disk that includes a spiral arm structure and a central bulge. (When they think of the shape of the Milky Way, they are often really thinking of the Andromeda galaxy, our neighbor in the local galaxy group.) The Milky Way actually has more of a bar structure. And ours is the one galaxy that you can’t find a good portrait of online anywhere.

Elliptical galaxies, as the name implies, are elliptical in shape. This other common galaxy type includes galaxies that might be much more massive than spirals. Ellipticals have no active star-forming regions like those found in the arms of the spiral galaxies. They also tend to have older stars and appear yellower in photographs.

This monthThree of the brightest galaxies in the sky are toward the north. The Andromeda galaxy is the faint fuzzy patch you can see between the “W” of Cassiopeia and the swooping “V” of Andromeda. It is low in the northwestern sky and setting by 10 p.m. The pair of galaxies M81 (Bode’s galaxy) and M82 (the cigar galaxy) are now as high as they get. They will be 20 degrees directly over Polaris at 11 p.m. I will save my list of favorite southern galaxies for next month.

Venus is now the evening star. For the next few days, Mercury can also be seen close to Venus in the evening sky. Saturday night, Mercury is a little more than 3 degrees above and to the right of Venus, but both will set within an hour of sunset. On March 28, Venus will appear very close to Uranus. This is one of the closest conjunctions I can remember but won’t be as impressive as many because Uranus is so dim. Even though you can easily see Uranus with your naked eyes on a dark clear night, you will likely need binoculars to see it because Venus is so much brighter and because it is so soon after sunset.

Jupiter is rising before midnight but is still best viewed if you get up early in the morning. It will be the brightest thing in the southwestern sky before dawn. Saturn and Mars are also morning objects. They are both passing through the brightest part of the Milky Way in the direction of Sagittarius.

Charles Hakes teaches in the Physics and Engineering Department at Fort Lewis College and is the director of the Fort Lewis Observatory. Email him at hakes_c@fortlewis.edu.

Useful links

Astronomy picture of the day: http://apod.nasa.gov/apod/
An Astronomer’s forecast for Durango: http://bit.ly/2eXWa64
Old Fort Lewis Observatory: www.fortlewis.edu/observatory
Four Corners Stargazers:
http://bit.ly/2eUqRJXhttp://bit.ly/2iGQPTbhttp://bit.ly/2igOSMc

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